Similarly, the "Enigma" code of the Germans had been broken by the British and was used with good effect against them.
This is generally considerded quite a feat of codebreaking.
However, the bone I wish to pick here is:
Why did both the Japanese and Germans use a breakable code at all ??? Were they brainless? Why would anyone charged with the responsibility of conducting warfare consider exposing their efforts to ruin by giving their enemies a 'fair chance'. For that matter, do the United States Armed Forces use breakable codes? CIA ... NSA ... ?? If so ... WHY ???
Here let me state a fundamental conjecture of mine. It goes across the board, through any discipline I have encountered.
The "experts", in any field of endeavor, do not consciously know the fundamental principles of their craft.This applies to mathematics, physics, medicine, engineering, whatever. I mean virtually, everything. I say this because I keep coming across things that seem to obviate whatever people are presently doing.
Am I on the correct planet here ???
Both the Japanese and German codes were "text" codes. That is, the fundamental element of a message was a letter or number for which a cipher was devised.
A "graphic" code differs in that the fundamental message element is the pixel. Thus, in a black and white message (with same numbers and text) sent in graphic code, the cypher consists of scrambled black or white dots which need to be assembled by the recipient in the correct order.
Such codes, properly made, are indecipherable IN PRINCIPLE.
To see why, observe this demo ...
The reason that a message thus scrambled is indecipherable is that the pixels can be rearranged into billions of meaningful messages. That is, in this example, 10x20=200 makes 2^200 permutations or about 10^60 (more than the number of attoms in the sun?) of which gadzillions of meaningful pictures can be formed.
A text cypher will generate less overall permutations and most importantly perhaps only several meaningful messages. (And if the cypher is simpler than the entire message - which is generally the case - only one meaningful message.)
Hence, God cannot in principle decipher such a simple code (from the coded message itself) and if He cannot neither can anyone else.
Even if you give someone both the scrambled and the unscrambled messages he couldn't decode subsequent messages because there is no way to tell which black pixel goes to what position in the unscrambled text because each black pixel is indistinguishable from another.
This type of coding is not for public / private key systems.
An inconspicuous code block (the Presidential Code) is put on the bill (one "message" for each bill). To see if a bill is real or counterfeit, decode the random dot pattern with a "P-code analyzer" to see the serial number of the bill. A match means that it is either real or an exact copy of a real bill.
This won't stop all counterfeiting but it should stop the Iranian mass production since they would be forced to acquire a real bill to counterfeit on a one for one basis. (Mass production on that scale requires that there be no restriction on the numbering of bills.)